In medium or high voltage switching element gear conductors are typically connected to a power rail or busbar through switches. These switches have at least two contacts which can be brought in contact with each other. As the voltages are high, these contacts need to be operated by a mechanism to safely bring the contacts in contact with each other. The mechanism typically uses a driving rod to drive one of the contacts to the statically arranged other contact.
The switching element itself can be insulated by surrounding the switching element with a sufficient layer of insulating material, such as air. This prevents flashover from the switching element to the outside world of a switch, like the housing. However, the driving rod will provide a bridge between the switching element and the housing. To prevent short-circuiting or flashover, the driving rod is at least partially made of an insulating material.
In optimal conditions the driving rod does not provide any problems with regard to flashover. However, when the insulating gas, like air at ambient conditions, used for insulating the switching element is humid, condensation could occur on the driving rod. This condensation reduces the insulation properties of the driving rod and could lead to flashover. Also pollution of the driving rod could reduce the insulation or provide concentrations in the electrical field, which also could lead to flashover.